dma: further decompose CopyRequest, so that each CopyRequest includes a single instance pair
dma: further decompose CopyRequest, so that each CopyRequest includes a single instance pair

StanfordLegion/legion,StanfordLegion/legion,StanfordLegion/legion,StanfordLegion/legion,StanfordLegion/legion,StanfordLegion/legion,StanfordLegion/legion,StanfordLegion/legion